It's said to be the best burger in Britain – served from a van on a London industrial estate. And it's part of a revolution in British street food, reports Jon Horsley

A well-dressed couple are picking their way through a grimy car park by a plumbers' merchant in Peckham, south London. "This is an industrial car park," says the woman, correctly. "Are you sure we should be here, darling?"

"No, I'm not, damn it," frets her partner. "But it's somewhere around here."

"This bloody burger van," says the woman, "had better be worth it."

The pair of foodies have travelled out of their comfort zone to make a long trek to The Meat Wagon, a burger van – but not like the ones you may know, selling mashed-up cow's anus, breadcrumbs and blood, defrosted and fried in dirty old oil. This is a different story all together: burgers from The Meat Wagon have their fat calculated to the closest percentage point. Ingredients are sourced from London's best producers and don't contain a single item that hasn't been researched, adapted and tasted repeatedly by the chef before serving. Their maker tried more than a thousand types of cheese before settling on one and has crossed continents to work out the science behind the perfect bun.

The £5 burgers are causing a sensation in food blogs. The influential Willeatformoney. blogspot.com says the elusive Peckham burger "blows all the competition out of the water" and Cheesenbiscuits.blogspot.com, voted one of the top 10 blogs in the country, describes The Meat Wagon's offerings as "a monumental achievement". News of the burger van's cult has even hit America with – Ahamburgertoday.com, the bible of meat sandwiches, praising "the slightly nutty and impossibly juicy meat". More promising still, these burgers could be a sign of a new wave of British food. After years in the gutter, there are the beginnings of a serious street food revolution in this country.

But back to our burger-van Blumenthal. The Meat Wagon owner is Yianni Papoutsis. A half-Greek boy from deepest Norwood, with no professional kitchen experience at all, he makes an unlikely burger expert but Papoutsis is obsessed.

Perched on a packing crate, he's delighted to expound on his ingredients. "We use 28-day aged prime chuck steak," he says. "It is well hung and then freshly minced each morning, quite thickly so you still get texture. It only lasts a day – we make meatloaf or chilli with any left after that. With the increased surface area [taken up by a burger], the meat leaches out so much blood that you don't get the same juiciness. You cannot serve a rare-ish burger with mince that's over a day old."

The Meat Wagon tried out patties that were 20 per cent fat – the level of most gourmet burgers – but with their coarse-ground mince and rare burgers, there were concerns about fat globules, so in conjunction with a butcher, they began experimenting. Trimming away, mincing and cooking until they found the perfect fat level – about 15 per cent.

The meat is only the start of the intricate calculations. The bread for the buns is an ongoing experiment. After months of research in America, Papoutsis found his desired bun. He disregarded the possibility of a brioche, which is favoured by upmarket restaurant burgers, as it fell apart after the first bite. He's been working with a local baker for about a year to create the ideal roll. They use a mild, sweet sourdough which works to cut through the richness of the cheese – and Papoutsis keeps daily tabs on it. "I tell [my baker] how the finished product works and he changes the steam-to-weight ratios and things like that," says Papoutsis. "The ones today are a tiny bit too soft."

His cheese is readily available but he won't reveal where from. Each burger is formed in front of the customer and after flipping, the pre-sliced cheese is added. It is then cooked under a cloche to melt it correctly. And this is not just any cheese. "I began with mature cheddar," he says. "I steamed it so it mixed properly and it looked fantastic – but it overpowered the meat. It was all you could taste and that's not what that burger is about, so we moved on. You need to get the right level of a property called hyperplasticity. It means that it melts into the crevices of the meat, which is hard to find outside processed cheese. I must have eaten a thousand types and some of them were horrible. At one point, literally every time I saw a new type of cheese slice, I bought it, whether it was a Turkish deli, Polish supermarket or farmers' market. It drove my other half mad and it was not easy on my stomach. I won't tell people what I use because they haven't suffered like I've suffered. But we've got the right one. A real cheese but with a good element of hyperplasticity. The idea is that the whole burger works together. It's an amalgam of the ingredients. That's something McDonald's does really well in the Big Mac. You don't taste bits, you taste the whole. No matter what you think about McDonald's – you can't argue with that. When you bite into a Big Mac, it tastes unmistakably like a Big Mac. You have to slow down and think about the separate flavours to notice things like the sauce and onions."

To finish off the classic cheeseburger there is French's Mustard – ("Obviously you wouldn't want it on your roast beef, but it is just the right tartness for this") – and Heinz Ketchup ("There's only one, isn't there?") and shredded iceberg and red onion ("texture"). Tomatoes cannot be trusted. "I just can't find a tomato in Britain that is tasty enough to stand up," he says. "There's no advantage in texture and there's no advantage in flavour."

You may be lucky enough to find that The Meat Wagon has left its Peckham car park – a friend owns the warehouse – and travelled to a pub or a festival near you. Despite the fact he calls himself a "guerrilla dining operation", it is important to Papoutsis and his team that their high-quality food is available to anyone who can find them. It's a common complaint of foodies that great cuisine in Britain is exclusively found in expensive restaurants in posh pockets of towns. For example, Gordon Ramsay claims that Britain has miles to go before it becomes a great culinary nation because food is not enjoyed from "the bottom up". He compares mass-produced sandwiches at our service stations to the rare roast beef that can be found in their French equivalents. This could be changing. The Meat Wagon is part of a collective called eat.st, made up of gourmet cooking vans including Gujarati Rasoi, a mother-and-son team cooking classical Indian food; Mexican vendors Luardos, who serve fiery fresh burritos not dimmed for the Western palate; and Choc Star, a van run by Petra Barran, a chocolate maker trained by master chocolatier Pierre Marcolini, who sells gourmet cocoa treats such as Mexican hot chocolate and some of the finest ice-cream you can eat. The success of these vans – in big demand on the festival circuit as well as markets up and down the country – could be a sign of that "bottom up" revolution. Petra Barra certainly believes that the vans and a new era in street food could have a role to play in British food culture.

"We reclaim urban spaces," she says. "You park up somewhere in a car park or outside an office block and suddenly that space belongs to everyone. People are outside their office eating and mingling – sharing an experience. It proves that good food doesn't have be stuck away in Michelin restaurants with menus that most people don't understand."

One big fan of Choc Star and Luardos is Simon Majumdar, street food expert and author of Eat My Globe. He's based in Los Angeles, where so-called "roach coaches" selling cheap food to Mexican workers, began the food van trend in the early 1970s. But though he's positive about the eat.st vans, he's more sceptical about the idea of a street food revolution. "Don't forget that street vendors selling food is a tradition dating back to 18th-century costermongers who sold pies and eels," he says. "There are good trucks and bad trucks; some succeed and some fail. The best ones will, in my opinion, eventually be bankrolled to open permanent bricks and mortar spots and the bad will disappear. Still, there are more and more of them – a consequence of high rents and high failure rates."

The Meat Wagon was inspired by roach coaches and fear of investing in a restaurant. Having travelled the world for 15 years as a ballet mechanist for the English National Ballet, Papoutsis found he had time off and £4,000 in an ISA. "My friends kept telling me to open a restaurant – but I'd seen all those Gordon Ramsay shows where people don't know what they are getting into and end up in loads of debt, crying in their beds after six months. I didn't want to be one of those idiots. So I bought a van. Most of the money went on a 40-year-old cast iron griddle. I had to go to America to find one that was heavy enough. You need to get one that gets really, really hot to get that lovely caramelised crust on the meat." And it seems to have paid off: "Three weeks after we opened," he says, "people were coming from all over."

So if he wasn't making his own burgers, where would he be eating them? "I do love a Big Mac," he says, "or a Double Double from In-N-Out, a West Coast American burger chain. The sauce contrasts with the burger really well. There's a sweet and sour element to the sauce that's almost addictive. Or there is a small place called The Apple Pan in LA."

By this time, the foodie couple who'd looked so incongruous in the Peckham car park have eaten.

"I never thought we'd find you," says the woman. "Thank you so much."

"Oh, no problem," says Papoutsis. "That's no problem at all."

As they walk away the couple have the glazed eyes of religious converts.

WHERE TO EAT ON THE STREET

Gujarati Rasoi

Mother and son Lalita and Urvesh serve authentic Gujarati food. Stall specialities are the traditional Thali, Samosa Chaat and Chunna Butteta. Find them at Exmouth and Broadway Markets. Gujaratirasoi.com



Brewed Boy

The newest addition to Soho's coffee scene, Brewed Boy's coffee cart is located on Rupert Street and uses Square Mile coffee to make his high-class brew. Brewedboy.wordpress.com



Jamon Jamon

Located on Portobello Road, Jamon Jamon produce freshly made paella. A taste of Spain but using the finest British produce. Jamonjamon.co.uk



Souper Stew

Run by Giles Smith and James Cantlon, Souper Stew is a relative new-comer to the festival and market scene. They trade in a reclaimed caravan and only use 100 per cent biodegradable packaging. Souperstew.co.uk



La Grotta Ices

Kitty Travers used to design the dessert menu for Fergus Henderson at St John. Now she sells icecream from a van, specialising in unconventional flavour combinations such as pumpkin mini-milk and rice & cinnamon. Lagrottaices.tumblr.com

Neha-Tamara Patel and Jenny Cosgrave

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